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Blood Thickening in Dogs

Polycythemia Vera in Dogs

Polycythemia vera is a condition where the blood thickens because the bone marrow produces too many red blood cells. This disorder typically affects older dogs.

Symptoms and Types

Symptoms and types of polycythemia vera manifest gradually but persist chronically and include:

  • Weakness
  • Depression
  • Lack of appetite (anorexia)
  • Redness of the skin (erythema)
  • Increased thirst and urination (polydipsia and polyuria)


While the thickening of the blood results from heightened red blood cell production by the bone marrow, the specific reason for this excessive production remains unknown.


To diagnose polycythemia vera in your dog, provide your veterinarian with a detailed history of your dog’s health, including when symptoms started and their nature. Your veterinarian will conduct a thorough physical examination and order a series of tests including a biochemistry profile, urinalysis, and complete blood count (CBC). Blood tests typically reveal an increase in red blood cell mass, with about 50 percent of dogs also showing an elevated number of white blood cells (leukocytosis).

To assess kidney and cardiopulmonary function, X-rays and abdominal ultrasounds will be performed. Echocardiography will evaluate cardiac functions. Additionally, your veterinarian will take a bone marrow sample for further examination by a veterinary pathologist.


Initially, the veterinarian will withdraw a significant amount of blood and replace it with intravenous fluids to reduce the viscosity of the blood. However, this provides only temporary relief. Long-term therapy, for both animals and humans, involves the use of an antineoplastic medication called hydroxyurea, which helps suppress the overproduction of red blood cells in the bone marrow.

Living and Management

Throughout the treatment process, your veterinarian will require regular follow-up examinations for your dog, particularly when administering hydroxyurea, as it may occasionally lead to bone marrow suppression. Additionally, adhere to the dosage recommendations provided by the veterinary oncologist when using chemotherapy medications like hydroxyurea, as these drugs are highly toxic.

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